--- a none object
none = none or function()
 return none
end

datatable_mt = {
  __index = function(t,k) return rawget(t,tostring(k)) or none end,
  __newindex = function(t,k,v) rawset(t,tostring(k),v) end,
}

datatable = function()
  local dt = {}
  setmetatable(dt,datatable_mt)
  return dt
end
